1. Field of the Invention
The present invention relates to a semiconductor device and a manufacturing method therefor which are applied to the fabrication of electronic equipment. More particularly, it relates to a semiconductor device wafer for incarnating the ultrathin and light construction of electronic equipment, as well as a semiconductor device having a structure in which such wafers are mounted in three dimensions (namely, in multilevel fashion), and a method of manufacturing the semiconductor device wafer as well as the semiconductor device.
2. Description of the Related Art
In order to promote reduction in the size of electronic equipment still further, it becomes an important point how the mounting density of semiconductor device components is heightened. Regarding also semiconductor ICs (integrated circuits), high-density mounting techniques, such as flip-chip mounting, in which an LSI (large-scale integrated circuit) chip is directly mounted on a printed-wiring circuit board alternatively to conventional package mounting, have been vigorously developed in the business world.
One of connecting methods based on a flip chip is a method wherein solder ball bumps are formed and mounted on the Al (aluminum) electrode pads of a semiconductor IC. A method of forming the solder ball bumps on the predetermined electrodes, employs electroplating. This method has the problem of being basically difficult to form the solder ball bumps of uniform heights within an IC chip because the thickness of a solder film to be formed is affected by slight dispersions in the surface state and electric resistance of a subbing material layer.
Dispersion in the heights of such solder ball bumps can be suppressed by a pattern forming method which employs the formation of the solder film by vacuum evaporation and the lift-off of a photoresist film. An example of a process for forming the solder ball bumps in accordance with this method, is illustrated in FIGS. 1A-1E of the accompanying drawings.
FIGS. 1A-1E are sectional views showing a method of forming solder ball bumps on Al electrode pads.
First, as shown in FIG. 1A, a film of Alxe2x80x94Cu (copper) alloy or the like is deposited on a semiconductor substrate 1 of silicon or the like by sputtering, and it is etched, whereby each Al electrode pad 2 is formed on the semiconductor substrate 1. Subsequently, the whole surface of the semiconductor substrate 1 including the Al electrode pads 2 is covered with a surface protective film 3 which is made of silicon nitride, polyimide or the like, whereupon the surface protective film 3 is formed by etching with each opening 3a which overlies the electrode pad 2. Subsequently, each BLM (Ball Limiting Metal) film 4 is formed in the opening 3a and on the surface protective film 3 by sputtering. Thus, each joint portion of a flip-chip IC is formed. Incidentally, the BLM film 4 is a multilayer metal film which is made of at least two of Cr (chromium), Cu, Au (gold), etc.
Thereafter, as shown in FIG. 1B, a resist pattern 6 which has each opening 5 overlying the BLM film 4 is provided on the surface protective film 3. Subsequently, as shown in FIG. 1C, an evaporated solder film 13 is formed on the whole surface of the resulting structure including the interior of each opening 5.
Thereafter, as shown in FIG. 1D, the unnecessary part of the evaporated solder film 13 is removed together with the resist pattern 6 by lifting off this resist pattern 6, whereby the desired pattern of the evaporated solder film is formed on the BLM films 4. Subsequently, as shown in FIG. 1E, the solder of the evaporated solder film is molten by a heat treatment, whereby each refractory solder ball bump 14 is finally formed on the corresponding BLM film 4.
The device chip formed with the bumps by employing the process proposed by the inventors as explained above is mounted on a printed-wiring circuit board by flip-chip mounting. Then, a mother board can be made smaller than in case of mounting a conventional device packaged with a molding resin. Therefore, the inventors have contributed to the incarnation of the smaller and lighter constructions of various electronic equipment.
Nevertheless, the mounting space of a semiconductor device should be reduced to the utmost for each of portable electronic equipment including an IC card, a portable telephone, a PDA (Personal Digital Assistant), etc. Accordingly, it is earnestly desired to establish a stacked (or multilayer) three-dimensional (or multilevel) high-density mounting technique which can make the semiconductor device still thinner in the height direction thereof, in addition to two-dimensional (or areal) space saving which has heretofore been mainly aimed at.
The present invention has been made in consideration of the circumstances as stated above, and has for its object to provide a semiconductor device and a manufacturing method therefor according to which the stacked ultrathin three-dimensional (or multilevel) mounting of semiconductor device components can be realized at a high reliability and with a high functionality.
In order to accomplish the object, a method of manufacturing a semiconductor device according to the first aspect of performance of the present invention is characterized by comprising the step of preparing a semiconductor device wafer which is formed with an LSI; the step of working the semiconductor device wafer from a back surface thereof, thereby to diminish a thickness of said semiconductor device wafer to at most 200 [xcexcm]; the step of forming a penetrant hole in the resulting semiconductor device wafer; and the step of forming a wiring plug in the penetrant hole.
A semiconductor device according to the second aspect of performance of the present invention is characterized by comprising a semiconductor device wafer which is formed with an LSI in its front surface, and which has been worked from its back surface, thereby to diminish its thickness to at most 200 [xcexcm]; a penetrant hole which is formed in the semiconductor device wafer; and a wiring plug which is formed in the penetrant hole.
A method of manufacturing a semiconductor device according to the third aspect of performance of the present invention is characterized by comprising the step of preparing a semiconductor device wafer which is formed with an LSI, and an electrode pad lying at a peripheral edge of the LSI; the step of working the semiconductor device wafer from a back surface thereof, thereby to diminish a thickness of said semiconductor device wafer to at most 200 [xcexcm]; the step of coating both a front surface and the back surface of the resulting semiconductor device wafer with an insulating material; the step of forming a hole which penetrates through coatings of the insulating material, the electrode pad and said semiconductor device wafer, by laser processing; and the step of forming a wiring plug for joining the front and back surfaces of said semiconductor device wafer, in the hole. Besides, as a working method in the case of working the semiconductor device wafer from the back surface, any can be employed as long as it is a working method adapted to thin the wafer. It is favorable, however, to employ grinding, chemical mechanical polishing, or etching by way of example.
With the method of manufacturing a semiconductor device in the third aspect, each of the surfaces of the wafer before the laser processing is coated with the insulating material in advance, whereby at the step of forming the microscopic penetrant hole in the thin wafer by the laser processing, the tapering angle of the penetrant hole can be restrained from widening at that opening end of the surface to-be-processed which a laser beam enters. As a result, the penetrant hole having a more perpendicular (or less tapering) sectional shape can be stably formed, and the penetrant hole joining the front surface and back surface of the wafer can be formed at a high precision. It is accordingly possible to form the wiring plug for directly stacking and mounting the semiconductor device. It is therefore possible to mount semiconductor device components by thin high-density mounting which serves to incarnate the ultra-small and ultrathin implementation of an electronic equipment.
The method of manufacturing a semiconductor device in the third aspect of performance should preferably further comprise after said step of forming said hole, the step of coating both the surfaces of the resulting semiconductor device wafer with an insulating material again, thereby to fill up said hole with the insulating material, and then forming a penetrant aperture having a diameter smaller than that of said hole, in said insulating material contained in said hole.
With the preceding method of manufacturing a semiconductor device, after the formation of the hole which penetrates through the semiconductor device wafer, both the wafer surfaces are coated with the insulating material again, thereby to fill up the hole with the insulating material, so that the penetrant aperture being smaller in diameter than the hole can be subsequently formed in the insulating material contained in the hole. Thus, the insulating material can be left on the inside wall of the hole so as to have a uniform thickness. Incidentally, after both the wafer surfaces have been coated with the insulating material again, the thickness of the insulating material on each of both the wafer surfaces is adjusted by polishing or the like as may be needed, whereby the work of the penetrant aperture at a higher precision can be stably carried out.
In addition, the reasons why the insulating material is left on the inside wall of the hole at the uniform thickness are to reliably insulate the wiring plug and the semiconductor device wafer, when the wiring plug which joins the front surface and back surface of the semiconductor device wafer is formed at the later step, and to reliably prevent electric current from leaking from the wiring plugs for connecting stacked semiconductor device chips, when the device chips have been stacked and mounted later.
A method of manufacturing a semiconductor device according to the fourth aspect of performance of the present invention is characterized by comprising the step of preparing a semiconductor device wafer which is formed with an LSI, and an electrode pad lying at a peripheral edge of the LSI; the step of working the semiconductor device wafer from a back surface thereof, thereby to diminish a thickness of said semiconductor device wafer to at most 200 [xcexcm]; the step of coating both a front surface and the back surface of the resulting semiconductor device wafer with an insulating material; the step of forming a hole which penetrates through coatings of the insulating material, the electrode pad and said semiconductor device wafer; the step of coating both the surfaces of the resulting semiconductor device wafer with an insulating material again, thereby to fill up said hole with the insulating material; the step of forming a penetrant aperture having a diameter smaller than that of said hole, in said insulating material contained in said hole, and simultaneously leaving said insulating material on an inwall of said hole; the step of forming wiring layers which join the interior of said penetrant aperture and the front and back surfaces of said semiconductor device wafer; and the step of patterning the wiring layers, thereby to form a wiring plug which includes respective electrode pads on said front and back surfaces of said semiconductor device wafer, and which joins said front and back surfaces of said semiconductor device wafer.
In the method of manufacturing a semiconductor device in the fourth aspect of performance, the wiring plug should preferably be formed by subjecting the semiconductor device wafer to electroless plating and electroplating in succession.
With the preceding method of manufacturing a semiconductor device, the thinned semiconductor device wafer is first subjected to the electroless plating, thereby to form thin seed layers of metal (for example, Cu) on the wafer surfaces including the inwall of the penetrant aperture. Thereafter, the resulting semiconductor device wafer is subjected to the electroplating by employing the seed layers as electrodes, whereby the metal wiring layers are formed on the whole wafer surfaces while filling up the penetrant aperture. Besides, resist patterns are respectively formed on the metal wiring layers by lithography, and both the wafer surfaces are subjected to etching with an etchant, whereby the wiring plug which joins both the surfaces of the semiconductor device wafer is formed, and the electrode pads for stacked (or multilayer) mounting are formed at both the ends of the wiring plug.
In the method of manufacturing a semiconductor device according to the third or fourth aspect of performance of the present invention, the insulating materials should preferably be made of a liquefied resin or an organic resist material. Favorable as the liquefied resin is an epoxy type resin, a silicone type resin, a phenol type resin, or the like.
A method of manufacturing a semiconductor device according to the fifth aspect of performance of the present invention is characterized by comprising the step of preparing a semiconductor device wafer which is formed with an LSI; the step of working the semiconductor device wafer from a back surface thereof, thereby to diminish a thickness of said semiconductor device wafer to at most 200 [xcexcm]; the step of forming penetrant apertures in the resulting semiconductor device wafer; the step of forming wiring plugs in the respective penetrant apertures; the step of dicing said semiconductor device wafer, thereby to be divided into semiconductor chips each of which includes the wiring plugs; and the step of stacking and mounting at least two of the semiconductor chips over a printed-wiring circuit board through connection means connected with said wiring plugs.
With the method of manufacturing a semiconductor device in the fifth aspect of performance, the thinned semiconductor device wafer is split into the semiconductor chips, and at least two of the semiconductor chips can be stacked and mounted over the printed-wiring circuit board. Here, it is possible in principle to stack and mount any number of semiconductor chips in multistage fashion. Moreover, since the chips have been subjected to the thinning work beforehand, the mounting height of the semiconductor device can be suppressed low even when the chips are stacked in the multistage fashion. It is accordingly possible to provide a semiconductor device module having a high functionality.
In the method of manufacturing a semiconductor device in the fifth aspect of performance, the connection means should preferably be at least one of a solder ball bump, a wire bump, an anisotropic conductive film and a conductive paste.
A semiconductor device according to the sixth aspect of performance of the present invention is characterized by comprising a printed-wiring circuit board which is furnished with lands on its front surface; and a plurality of semiconductor chips each of which has a thickness of at most 200 [xcexcm], and which are stacked and mounted over the printed-wiring circuit board through connection means; each of the semiconductor chips including penetrant apertures which penetrate through said each semiconductor chip, and wiring plugs which are respectively formed in the penetrant apertures; the lands and the wiring plugs being electrically connected by the connection means, respectively.
By the way, the present invention is very effective for manufacturing a future semiconductor device of which a high functionality, a high reliability, a small size and a light weight are required.